The invention relates to solid electrolyte measuring cell devices of the type commonly referred to as oxygen sensors which are suitable for use in the exhaust path of an internal combustion engine. More particularly, the invention relates to a mounting and sealing arrangement for oxygen sensors of the so-called wafer or disc type wherein the solid electrolyte, which is preferably stabilized zirconium oxide, is in the form of a thin disc or wafer having a porous electrode coating on each side. A voltage is generated between the electrodes when there is a difference in oxygen partial pressures between the exhaust gas side of the electrolyte and the reference, or air side. Since the electrical signal is a maximum when the engine is operating stoichiometrically and combining all its CO with all of the excess oxygen, the sensor can be used as part of an air/fuel ratio control system to minimize pollutants. Examples of such wafer type sensors can be found in Carnahan et al U.S. Pat. No. 3,768,259 and in copending application Ser. No. 394,431, filed Sept. 4, 1973, each of which is assigned to a common assignee. Other wafer type sensors are disclosed in Van Esdonk et al Patent 3,819,500 and in East German Pat. No. 21,673 issued Apr. 7, 1961.
Despite the prior art attempts to achieve a durable oxygen sensor which will have a long life in the rugged environment of an automotive exhaust stream, problems such as seal leakage caused by the extreme temperature range experienced in the exhaust stream, electrical short circuits, lead breakage, and expensive construction techniques have combined to prevent the development of a durable and leak-tight sensor which can be produced in mass production at a relatively low cost. Auto manufacturers and others have developed electronic systems to process the information produced by an oxygen sensor as well as other systems to use the sensor information to control the operation of an engine to achieve maximum performance, fuel economy and freedom from exhaust pollutants. It would therefore seem to be most desirable to have an exhaust gas sensor which overcomes the durability and sealing problems of prior art structures and which can be made in mass production to high standards of uniformity.